The present invention relates to a Doppler radar speed sensing system.
It is well known that the speed of a moving object, such as a vehicle, can be measured by means of a Doppler radar system. For example, microwave Doppler radar systems have been used on vehicles to measure their ground speed. A conventional technique in such systems is to utilize a phase-lock-loop, PLL, as part of the signal processing circuitry. Such a PLL generates a signal with a frequency which is approximately the average of the frequency of an incoming Doppler signal. However, such radar systems with PLLs respond slowly to changes in vehicle speed and produce errors in accuracy. For example, the quality of information contained in the PLL generated signal may be degraded by momentary Doppler signal loss due to the composition and condition of the terrain over which the vehicle is traveling. Degradation may also be caused by the random nature of the Doppler signal and by the presence of some moving objects in the field of view of the antenna.